Method and apparatus for increasing recovery from oil sands



Oct. 29, 1935.

W. E. LANG METHOD AND APPARATUS FOR INCREASING RECOVERY FROM OIL SANDS I Filed April 24, 1935 u a o a n.

u a a g n a e a Q a ne v 'ggg 2 sheetssheet 1 Oct. 29, 1935. w. E. LANG 2,019,418

METHOD AND APPARATUS FOR INCREASING RECOVERY FROM OIL SANDS.

Filed April 24, 1935 2 Sheets-Sheet 2 STA-ES METHOD AND APPARATUS FOR DIG-RECOVERY FROM OIL William E. 2 V:

Application April' 24, 1935, Serial No. 18,959

My invention aims to provide a method and apparatus for more efllclently operating pressure wells to secure a greater recovery of oil from virgin and partially depleted sands than 'nas been possible with previous methods.

As is nowlwell known in the art, oil wells which have partly or wholly ceased producing, due to decline in the reservoir or rock pressure Within the oil bearing strata, may be revived by repressuring the strata. This is accomplished by utilizing a nearby well, or one drilled expressly for the purpose, and which passes through the same strata, as a pressure well into which air, gas, or water is forced under pressure and thence into the oil bearing strata. 'I 'he pressure oi' the fluid forced into the strata causes or increases a flow of oil from the strata to the producing Wells and thus increases the recovery of oil from the sands.

The oil which can be recovered without repressuring is estimated as being only `about lil-40% of the oil originally stored in the oil bearing sands, and hence the value .of representing is quite evident. However, repressuring as heretofore practiced does not and cannot result in either a complete or uniform recovery from the various oil bearing strata which go to make up a given sand or horizon, due to the lack of uniformity of resistance to ow offered by the dierent strata in the same sand or horizon and to the fact that all are' subjected to repressuring indiscriminately. l

An objectof the present invention is to provide y for selectively repressuring the several productive strata comprising a sand or horizon so as to obtain the maximum recovery of oil from each and hence from all, and thus to increase the total recovery.

My invention is also of great value for use in effecting a proper control of oil recovery from vigin or newly opened oil fields, so as to avoid depletion of highly permeable strata, and often the ooding of wells due to passage of water through such depleted strata into the wells, prior to depletion of oil in the less permeable strata l from which the oil normally ows more slowly.

' permeability or resistance to flow of the indii vidual strata of a sand and thus securing valuable 1s (c1. 16o-21) adapted to permit of selectively repressuring the E@ several productive strata of a sandl or horizon; the portion designated B illustrates in dlamatic manner a vertical section through a representative sand, showing the various strata and properties thereof, to indicate the mode of opera- 35 tion of the packer;` and the portion a :n

similarly illustrates a producing well into which the oil is caused to now from the sand;

Fig. 2 is a transverse section, broken away, of

spacing and orifice arrangement;

Fig. 3 is an enlarged view of a portion of the sleeve arrangement shown in Fig. 2; Y

Fig. 4 is a longitudinal cross-section of a pora rubber packer sleeve provided with a med m tion of a rubber packer sleeve provided with still 25 another spacing and oriiicearrangement;

Fig. 5 is a vertical elevation View of a metal packer sleeve;

Fig. 6 is a vertical elevation of a med form of metal packer sleeve; and

Fig. 'lis a transverse section of the sleeve sh in Fig. 6, taken on the line l-Jl.

Referring to Fig. 1, B, which shows the results of a core analysis of the Venango sand, Venango County, Pennsylvania, and indicates the percentage porosity and the permeability in millidarcys of lthe various barren and productive strata which make up the sand, it is evident that there is a very great variationin properties between strata inthe same oil formation. There are a number of productive strata (b, d, f; i, j, lc), anda number of barren strata (a, c, e, g., h) some of which are inter s between the productive strata. The productive strata which are adjacent each other (i, i, k) are'separated by 45 shalelaminations and hence may be treated as independent oi' each other. As indicated, some of the productive strata. are more highly productive than others, and the permeability oi' one of another (b).

My invention depends uponthe observed fact that the greater the permeability of a stratum the less the resistance to ilow of oil or other fluid productive stratum (o is about eighty times that 5 Queres Aty the mmm.' su, ses or water 55 introduced under pressure into the strata without control will, because of its nature, follow the lines of least resistance, a high rate of recovery of oil is effected from the highly permeable forced into a formation from a pressure well without regulation of the pressure, volume and velocity as between strata. This has been the practice heretofore, except as perhaps modified by the sealing off of a highly permeable and depleted stratum from which no further substantial recovery can be expected. The result is that a property may be repressured for several years with the recovery of oil from only `the more highly permeable strata and with little recovery from thek strata of low permeability. notwithstanding that the latter may be highly saturated withoil.

Furthermore, in fields having hydraulic control, the edge wells are flooded out before any substantial recovery of oil has been secured from the strata of low permeability, due to the ready iiow of water into the wells through the depleted strata of high permeability. For example, it is known that the water-flooding method practiced in the Bradford, Pennsylvania, fields, has produced only 35-40% of the oil remaining after the first recovery. This I believe is due to the fact that the water passes rapidly through the highly permeable strata, resulting in a low percentage of recovery from the less permeable strata prior to the fioodingvof the producing wells.

In accordance with the present invention, the energy supplied by repressuring is directed selectively into each of the various productive strata making up a sand or horizon so as to deplete the oil in each at a more nearly uniform rate. I have discovered that by regulating the pressure. volume and velocity of the repressuring fluid introduced into the several strata, so as to exert a greater force on oil in the less permeable strata than on oil in the more highly permeable strata, a more nearly complete recovery of the oil in all of the strata can be secured in any given period and no stratum need become exhausted before having obtained effective recovery from all.

Another great advantage of my method ls that less repressuring uid will be required per barrel of oil recovered due to the more efficient use of the repressuring fiuid, and hence recovery vcost will be greatlylowered.

According to my invention, I prefer to inject the repressuring fluid into the lower portion only of each productive stratum. This is the most highly saturated portion and the result is to move the oil most effectively with the least wastage of the repressuring fluid and to secure a maximum recovery of oil.

Illustrative apparatus for carrying out the invention is shown in Fig. 1A, and comprises a packer unit adapted to permit of lcontrolling the repressuring of each of several associated strata independently of each other. The packer unit is made to have an externalxdiameter substantially filling the bore of the well in which it is to be used, leaving about inch clearance from the well wall when not under pressure, and may be made in any reasonable and practical length to conform to the thickness of the pay sand.

If necessary, several units may be connected directly in series.

In the form of .the inventionl illustrated in Fig. 1 A,`at each end of a unit there are cylindrical steel head blocks I and 6, provided with in- 5 ternally threaded tubing seats to receive the threaded ends of the well tubing in which the unit is interposed in series. The end blocks are connected by a perforated steel pipe barrel 4,

Vhaving openings 9, which may be welded to inner shoulders thereof. A rubber sleeve 3 concentrically surroundspipe barrel 4 and is' secured and sealed at each end by being clamped against external shoulders of each head block by lock nuts Zand 5, respectively, which engage externally threaded portions of the head blocks.

Rubber sleeve 3 is provided with sets of cir- =-cumferential orifices or openings 1 so spaced along its length that a set of orifices will communicate with the lower portion of each of the productive strata in the sand for which the packer unit is designed, the sleeve being otherwise air tight. Raised bands 8 are secured around the sleeve to space the latter away from the well wall in proximity tothe orifices.

When air, gas, water or'other fluid is pumped under pressure into the well tubing, the packer unit being in operative position in the pressure well, the uid will pass through perforations 9 in pipe barrel l and will force the flexible sleeve I 3 against the well wall so as to eiect a seal at all portions except where the orifices are exposed to the sand strata.- A portion of the iluid will be forced into each productive stratum through the corresponding orices,-and once having passed through such orifices will be sealed off from all other exposed strata by the intervening sleeve pressed against the well wall. The uid will thus be forced into the lower portions only of each stratum, assuming the orifices to be o opposite such lower portions and n o orices opposite'the upper portions, due to the sealing acy tion of the sleeve.

By suitable variation in the size, number and arrangement of orifices as between the sets of orifices, each set corresponding to one stratum, it will be evident that the repressuring of each stratum can be controlled independently of the others and thus the desired results can be obtained in accordance with my invention.

Obviously many variations of the above described apparatus are possible. Thus, instead of perforated pipe barrel 4, rods may be used to secure and space apart end blocks I and 6 and permit access of the pressure uid to the sleeve. Sleeve 3 need not lbe made of rubber or even of a highly elastic material. A strong fabric, such as canvas, impregnated with rubber, may be used; or any suitable pressure resistant flexible material. The raised spacing bands 8 may be dis- 60 pensed with, and the orices may be provided with eyelets so contrived as to serve as spacing members.

Figs. 2 and 3 show a modified arangement for providing orices in rubber sleeve 3. A stiff metalg5 strip I0, which may encircle the sleeve, is fastened with rivets, I3 circumferentially of the sleeve at portions where orifices are desired. These strips are provided with corrugations II, which run longitudinally with respect to the sleeve, so as to space the sleevefrom the well wall th'ereat, and holes or other openings I2 in the sides of the corrugations permitthe fluid to pass through underlyingopenings I4 inl the sleeve to the strata outside.- -Openings may also 75 be provided in portions of the strips lying between the corrugations.

In Fig. 'i an optional arrangement is shown in which .the sleeve 3 is provided at appopriate 'places with a stiff metal band or ring 20, fastened to the sleeve by means of rivets 2|. This band is internally corrugated, the corrugations encircling the sleeve and having holes or other openings 22 in the depressions to permit of the desired fluid iiow. The sleeveis provided with openings 23 to expose the openings in the band to uid within the sleeve.

In the form of packer sleeve 3a illustrated in Fig. 5 which may be used in place of the rubber sleeve 3 shown in Fig. 1 and secured and positioned in the same manner, the sleeve is made of seamless drawn copper or other suitable metal having some capacity for stretching or expanding under-pressure before breaking or splitting open. At distances of every few inches, this metal sleeve is provided with interiorly projecting corrugations i5 which provide circumferential encircling grooves in the outer surface. Some or all of these corrugations are drilled, in accordance with the nature and arrangement of the stra'ta, to provide openings or orifices I6 to permit air or other fluid under pressure to pass through the sleeve and ll the annular spaces surrounding and adjacent to the corrugations inwhich such openings are located.

When the sleeve' is under pressure, as when strata are being repressured, the iiuid pressure within the sleeve Will force it against the well wall to provide longitudinal sealing. In addition, sealing bands Il of rubber or other suitable material may be placed in some or all of the unperforated corrugatio-n grooves to provide additional sealing action, such sealing bands being disposed With relation to the perforated corrugations so as to seal the various strata from each other as previously described.

Still another form of packer sleeve is shown in Figs. 6 and '7. Sleeve 3b is made of. metal and is provided with a multiplicity of longitudinal corrugations 25 which permit and facilitate the expansion of the sleeve under internal pressure independently of the stretchability of the metal itself. Holes 26 are drilled in the sleeve at suitable places to serveas orces and provide the desired selective injection of fluid into the strata as heretofore described. Sealing bands or rings 2l, of rubber or other suitable material, are disposed about the sleeve on either side of the various portions containing orifices so as to space them from the well wall, provide annular discharge zones, and seal the discharge zones apart. These sealing bands are made of resilient material and penetrate into the corrugatlons of the sleeve when compressed between the Well wall and the sleeve, the latter expanding under internal pressure so as to exert the necessary pressure on the sealing bands.

Fromthe foregoing description it will be evident that there are many possible embodiments of my apparatus invention and this description thereof is intended to illustrate my invention and not to limit the same.

The considerations affecting the actual design of a particular packer unit are of course many, and one form may be found more suitable under one set of circumstances and others under different circumstances. Thus the pressure of the fluid employed for repressuring mayvary in practice from 60 to 2500 pounds per square inch depending on the particular fluid, the nature of the strata, and the spacing of the pressure well from the producing wells, and a more readily expansible form of packer sleeve will be required the lower the pressure.

- The oil present in the pressure well to which 5 the packer is exposed, the pressure fluid itself, and the chemicals which may be contained therein to facilitate repressuring, will also impose de# sign restrictions, due to the necessity of avoiding excessive corrosion or deterioration. Thus a cop- 1o per packer sleeve, or one of special alloy steel, may be most suitable because of its resistance to certain types of corrosion, for example, where rubber cannot be efficiently usedyor vice versa.

Several packer units may be connected in a 15 'single string of Well tubing for serving different separated sands, or by the use of concentric strings of Well tubing they maybe supplied separately with repressuring fluid or fluids under different pressures. 20

No simple rule or formula can be given for determining the relative size and 'number offorices corresponding to each producing stratum of a sand. It will be apparent that the pressure, volume and velocity of the repressuring fluidl en- 25 tering each stratum will be dependent upon .a number of variables, including the permeability and degree of saturation-of the stratum, and its thickness, the character andnumber of orifices,

the supply pressure within'the packer barrel, the 30 nature of fluid used for repressuring, the well spacing pattern, and the oil content to be recovered.

However, knowing the relative permeabilities of the different strata, as determined by a core 35 analysis, a rough initial estimate `can be made which will result in greatly improving the repressuring of the sand, bearing in mind that the lower the relative permeability of a stratum the greater the energy that must be supplied in comparisonv 40 With strata of high permeability, other factors being equal. This is indicated in Figs. 1A and 1B, where the size of the orifices corresponding to stratum b, which has a very low permeability, is much greater than that of the orice corre- 45 sponding to stratum i, which has a very high permeability. After repressuring for some time vthe effects can be changed, as operating experience indicates, in order to secure even better uniformityof depletion as between strata. 50

Permeabilities as determined by laboratory core analysesare useful, but due to the fact that core samples represent only small portions of thev strata from which they are taken, the results obtained may not represent the effective perme- 55 ability of the strata with suflicient accuracy when considered in relation to the reservoir as a whole.

A more direct measurement of the effective permcabilities of different strata can be obtained 60 by use of the packer un't previously described, and the-results so obtained may advantageously be used in determining the relation of orifices for repressuring. For this purpose the packer unit may be constructed in the manner set forth, 65 but the' outer iiexible sleeve 3 should be provided with orifices in one region only, so as to provide orifices for only a short distance longitudinally, for example 6-10 inches. This packer unit, plugged at the bottom, is lowered on tubing into the desired position for testing, beginning at the bottom of the pay sands so that the orifices or perforations in the sleeve will be opposite the lower part of the stratum. Pressure is` then applied, the desired represxlrlng fluid,

- test.

The pressure is then released and the packer unit raised for a test of the next adjacent region inthe same manner, and similarly each foot or yfraction of the sand can be tested.

From the results so obtained, the eective permeabilities of the different strata making up the particular sand or horizon may be estimated and their relation to the reservoir as a whole ascertained. Thus the eillcient pressure and volume that the formation will take in its various strata can be determined, and from this information the size, number and arrangement of oriilces in the packer imit for repressuring can be estimated.

I claim the following as my invention:

1. "Ihe method of selectively controlling the recovery of oil from a sand having a plurality of associated productive strata oilering different resistances to flow of oil contained therein, which comprises injecting a fluid under pressure into each productive stratum of the sand, and independently regulating the injection into each stratum so as to'nore nearly equalize the rate of depletion of oil in the several strata Within a given period of time.

2. The method of selectively controlling the recovery of oil from a plurality of associated proi ductive strata in the same sand whichl normally become depleted at different rates, which comprises simultaneously injecting a iluid. under pressure int'o each productive stratum of the sand, and controlling the fluid energy thereby introduced .into the different strata of the sand according'to the diiferentresistances to flow of oil offered by each stratum.

3. The method of repressuring an oil sand having a plurality of oil containing strata, which comprises repressuring each productive stratum of the sand independently of the others and controlling the relative repressuring of the several strata.

4. The method of controlling the recovery of oil from a plurality of associated productive strata in the same'sand, which comprises injecting a fluid under pressure into the lowerportion only of each stratum of the sand and controlling the relative injection into the several strata.

5. 'I'he method of controlling the recovery `of oil from a sand having a plurality of associated productive strata of different permeabilities, which comprises simultaneously introducing a fluid under pressure from a common supply zone to exposed portions of each stratum at a place distant from a recovery well, and regulating the pressure, volume and velocity ofthe fluid introduced into each stratum of the sand to increase the comparative rate of recovery at the recovery well from the strata of lower permeability.

6. -The method of selectively supplying uid under pressure to several associated productive strata in the same sand to increase the recovery therefrom, which comprises first introducing a fluid under pressure to each stratum individually -and controlling the relative injections in accordance with the relative permeabilities previously 5 determined so as to increase the. comparative uniformity of recovery from the different strata of the sand. A

7. Apparatus for introducing fluid under pressure to several associated productive strata in the same sand, which comprises means for simultaneously supplying fluid to the several strata in the sand from a common supply zoneadapted to be located within the sand, and means for selectivelyl controlling the uid supply to the several individual strata of the sand independently of each other.

8. Apparatus for simultaneously and selectively introducing fluid under pressure to a plurality of neighboring .productive strata of a sand exposed in a pressure well, which comprises a iluid supply chamber of length coextensive with the several exposed productive strata and means for connecting the same to a well pipe for supplying fluid under pressure thereto, said chamber havlng openings communicating with the exterior, concentric means external of the chamber for sealing the strata from the fluid, and a plurality of passages through the sealing means for conducting fiuid from the supply chamber to the several productive strata simultaneously but independently of each other.

9. A pressure packer for use in a pressure well for repressuring a plurality of neighboring oil strata, comprising a fluid supply chamber and means for connecting the same to a well pipe, an expansible tubular sleeve surrounding the chamber and secured at the ends to prevent outow of fluid therebetween, said sleeve being adapted to press against the well Wall when under pressure, and openings in the sleeve spaced apart to correspond to the various strata to be repressured.

10. A pressure packer for use in a pressure well for determini-ng the permeability of individual oil strata in a sand having several associated 5 strata, comprising a fluid supply chamber and means for connecting the same to a well pipe, an expansible sleeve concentrically surrounding the chamber and secured at the ends to prevent outflow of fluid therebetween, said sleeve being adapted to press against the well wall when under internal pressure exerted by fluid in the supply chamber, and openings in the sleeve to permit flow of fluid to a localized region of a single sand only when the sleeve is pressed against the well under pressure to the interior of the sleeve, and

spaced passages for conducting and individually controlling the flow of the fluid from the interior of the sleeve. to the several productive strata.

12. A pressure packer for use in a pressure well for supplying iluid under pressure to a plurality 70 of neighboring productive strata. comprising an expansible tubular sleeve having a length coextensive with several productive strata and having openings to control passage of fluid from the interior of the sleeve to said strata, sealing rings encircling the sleeve at intervals to' provide separated annular fluid supply zones for the several strata externally of the sleeve, and means forv supplying iiuid to the interior of the sleeve.

13. A pressure packer for use in a pressure well for supplying uid under pressure to a plurality of neighboring productive strata, comprisinga. tubular sleeve having -a length coextensive with several productive strata and provided with longitudinal corrugations to facilitate expansion of the sleeve under internal pressure, and exterior sealing means dividing the outer surface of the sleeve into annular zones.

14. An oil eld repressuringsystem embodying means `for simultaneously supplying a pressure medium to each productive stratum of an oil sand containing a plurality of productive strata,

and means for controlling the volume and pressure of said medium supplied to each stratum to suit the resistance to flow therein, whereby rapid over-depletion of the more permeable strata of the sand is prevented and a more complete recovery from the sand is secured.

WILLIAM E. LANG. 

